Both municipal and industrial treatment of wastewater using an activated
sludge process generates large quantities of biosolids referred to as sludge.
Currently the Knoxville Utility Board (KUB) generates 65 tons/day of these
solids (dry basis) from their activated sludge wastewater treatment facilities.
This material is concentrated from 4.2 wt % up to 35 ? 40 wt % via filtration
and disposed off-site by trucking it over 70 miles for disposal through land
farming. Every year the distance becomes greater due to KUB?s inability to
find acceptable sites for land farming. At least several industries (DuPont
and Tennessee Eastman) have similar problems with sludge disposal. On site
destruction of the excess biosolids is preferred from both an economic and
environmental standpoint. Currently both Dupont and Tennessee Eastman use
on site incineration and would prefer a more environmentally benign process
which uses less energy. A nitric acid catalyzed hydrolysis process can convert
most of the sludge into a biodegradable material suitable for recycle. There
is also a possibility that the sludge could be converted into acetic acid
for commercial sale. The major products from this hydrolysis are organic acids.
It may be possible to optimize production of these acids to the point were
it is economically feasible to convert the waste activated sludge stream into
a commercial product. If it is not economically feasible to recover the organic
acids the stream can be recycled back to the waste treatment unit where the
organic acids will biodegrade.

This proposal will consist of a batch scale kinetic study using activated
sludge from KUB?s Kuwahee treatment facility, employing a factorial experimental
design. The variables consist of residence time, reaction temperature, solids
concentration, and nitric acid concentration; with percent conversion and
acetic acid concentration as the dependent variables. The concentration of
the sludge can have a significant impact on the economics of any potential
process and must be investigated. The sludge stream from KUB?s activated sludge
treatment process is 4.2 wt % and is concentrated to 35 ? 40 % by filtration
prior to land farming. A feed sludge concentration in the range of 4.2 - 40
wt % will be investigated. The data will be analyzed and a mathematical model
will be developed for the reaction kinetics over the range of the input variables.
The form of the model will depend on the experimental data. If significant
quantities of organic acids are obtained a complex model will likely be required;
if the organic compounds are not produced in sufficient quantity a much simpler
model describing destruction kinetics will be employed. The model will be
utilized to evaluate the economics of the process and to develop a preliminary
process design. A continuous pilot scale unit will be designed and built.
This unit will be used at KUB?s Kuwahee treatment facility in the second year
of the project.